Processes for preparing propylene oxide with the help of organic hydroperoxides are well known in the art. As described in U.S. Pat. No. 5,883,268, such process conventionally comprises peroxidation of ethyl benzene, followed by contacting the peroxidation reaction product with aqueous base in amount sufficient to neutralize acidic components thereof, and phase separating the resulting mixture into separate aqueous and organic phases. The organic phase containing ethyl benzene hydroperoxide can be reacted with propylene catalyzed by solid heterogeneous catalyst in order to obtain propylene oxide. U.S. Pat. No. 5,883,268 describes that severe catalyst deactivation in the propene epoxidation is prevented by water washing the organic phase in order to separate off the basic materials followed by stripping water from the resulting organic phase.
U.S. Pat. No. 5,723,637 describes a similar process for producing propylene oxide comprising autoxidation of ethyl benzene to obtain a raw material solution of ethyl benzene hydroperoxide in ethyl benzene which is reacted with propylene in the presence of a titanium containing solid catalyst to give propylene oxide. In order to suppress depression of activity of the titanium containing solid catalyst with the passage of time, the raw material solution is prepared by washing the solution of ethyl benzene hydroperoxide in ethyl benzene with an aqueous alkali solution to bring the lactic acid concentration to 5 ppm by weight or less. The oily phase obtained after the alkali washing may further be washed with water.
It has been found that in spite of washing the organic hydroperoxide with a basic aqueous solution of an alkali metal salt optionally followed by a water wash, there is still a considerable amount of contaminants present in the product. It has been found that washing with a basic aqueous solution of a metal salt, introduces metal ions in the organic phase. The contaminants, especially the metal ions, can lead to problems when further processing the organic hydroperoxide. If the organic hydroperoxide is to be used in the preparation of propylene oxide, metal ions in the organic hydroperoxide stream can lead to more rapid deactivation of the catalyst generally applied for preparing propylene oxide from propene.